Swash-plate drive for axial piston pumps/motors

ABSTRACT

The invention provides an axial piston pump/motor whose stroke is controlled by a tiltable swash-plate carried on a non-rotary tilt member by a thrust bearing wherein torque reaction to piston thrust and swash plate drive is transmitted directly to the pump/motor mainshaft by spherically jointed links.

United States atent [191 Clerk Oct. 14, 1975 SWASH-PLATE DRIVE FOR AXIALPISTON PUMPS/MOTORS [76] Inventor: Robert Cecil Clerk, Edison House,

Fullerton Road, Glenrothes, Fife, Scotland [22] Filed: June 15, 1973[21] App]. No.: 370,346

[52] US. Cl 91/499; 74/60 [51] Int. Cl. F01B 13/04 [58] Field of Search74/60; 91/499, 485; 417/218 [56] References Cited UNITED STATES PATENTS1,840,866 1/1932 Rayburn 91/506 2,151,415 3/1939 Bennetch 74/602,157,852 5/1939 Grosser 74/60 2,227,998 1/1941 Borer et al.... 74/602,256,952 9/1941 Sappington... 74/60 3,426,686 2/1969 Anderson 417/2183,495,542 2/1970 Kratzen 91/485 Primary Examiner-William L. FreehAttorney, Agent, or FirmLerner, David, Littenberg & Samuel [57] ABSTRACTThe invention provides an axial piston pump/motor whose stroke iscontrolled by a tiltable swash-plate carried on a non-rotary tilt memberby a thrust bearing wherein torque reaction to piston thrust and swashplate drive is transmitted directly to the pump/motor mainshaft byspherically jointed links.

2 Claims, 2 Drawing Figures FIGI Sheet 2 of 2 U.S.. Patent Oct. 14, 1975PEG. 2

SWASH-PLATE DRIVE FOR AXIAL PISTON PUMPS/MOTORS This invention relatesto a swash-plate drive for pumps and motors having axially movingpistons.

In axial piston hydraulic pumps where the length of stroke and movementof the pistons is effected and controlled by a swash-plate of variabletilt angle, it is normal practice for a driving shaft torque to betransmitted to the reactive swash-plate through the medium of amulti-cylinder barrel (splined or keyed to the driving shaft) and thepistons, the remote or cantilevered ends of which are fitted witharticulated shoes conforming to the swash-plate relative angularityduring each revolution of the barrel.

This system has several disadvantages, the more prominent of which are(a) the difficulty and cost of ensuring true alignment of the barrel onthe shaft and in relation to a matting port-face of the pump casingwhich controls the distribution of the pumped pressure fluid, (b) thevery high friction and poor wear resulting from the natural cantileveraction of the drive torque loading transmitted by the pistons and actingon the lip of the cylinder mouths, (c) the low mechanical efficiency ofa necessary articulated shoe accommodation to the swash-plate.

It is known to utilise articulated connecting rods between the pistonsand a rotating swash-plate member to improve disadvantage but with avariable tilt angle swash-plate it has still been found necessary totransmit the driving torque via the remote end of each piston bymechanical contact with a precisely located swelling on each connectingrod intermediate of its length between the *spherical" articulate ends.Unfortunately, this does not provide any appreciable alleviation of theloading transmitted to the cylinder mouth as in disadvantage (b).

The object of the present invention is to provide a method oftransmitting the driving torque directly between the mainshaft and arotating swash-plate, bypassing the rotating barrel, the cylinders,pistons and articulated connecting rods, which are thus able the betterto handle the axial pumping loads with only minor parasitic dragtorques. This applies not only to pumps but to hydraulic motors ofsimilar configuration, the difference being that in a motor the torquegenerated at the swash-plate serves to drive the mainshaft.

To this end what we propose is an axial piston pump (or motor) havingvariable tilt angle swash-plate stroke control and rotary port-facehydraulic distribution control, characterised by a rotary swash-platemember in which the piston-thrust torque reaction or developed torque onthe rotary swash-plate member is transmitted directly to the mainshaftby spherically jointed links inter-connecting that member to the shaft,the cylinder barrel being only indirectly located rotationally on themainshaft by a sleeve loosely keyed thereto, and the rotary swash-platemember being supported by a thrust bearing on a non-rotary tilt member.

However, a preferred arrangement utilises a universal spider in whichthe radial outward arms on the mainshaft and the radial inward arms ofthe rotating swash-plate are inter-connected as pairs by sphericallyjointed links. By designing the links as a flattened C, the orthogonalstub ends can be adapted to use commercially available spherical endunits with positive lubrication from a mainshaft gallery.

A preferred construction form of the invention is illustrated in theaccompanying drawings in which:

FIG. 1 is a central vertical cross-section showing a swash-plate at 25stroke angle;

' FIG. 2 is a plan view of the swash-plate at zero stroke angle.

The mainshaft l of an axial piston pump/motor is forged or castintegrally with three radial arms 2.

Each of the arms 2 is fitted with a part-spherical cup bearing 3 toreceive the stub end of a flattened C shaped link 4, one of which isshown in the drawings. These stub ends are extended with centrifugalbalance weights 5.

The opposite stub-ends of the links 4 are received in part-spherical cupbearings 6 in inwardly directed arms 7 of the rotary swash-plate 8.

The swash-plate 8 is carried in an annular thrust bearings 9 in thenon-rotational tilt member 18, which is tilted about trunnions 10 bycontrol levers (not shown) connected to lugs 11.

The part-spherical ends of piston rods 12 are received in cup bearings13 in the rotary swash-plate 8.

The pump/motor cylinder barrel l4, bolted to a sleeve 15 loosely keyedto the shaft 1 is shown supported from the pump/motor stator casing 16by a flanged keep nut 17.

Piston torque reaction (in the case of a pump) or developed thrust (inthe case of a motor) is transmitted to the shaft 1 through the medium ofthe rotary swashplate 8, links 4 and arms 2 (constituting a universaljoint) and end thrust is taken by the bearing 9 in the stationary tiltmember 18. Rotary port-face hydraulic distribution control is utilised.

I claim:

1. An axial piston pump/motor having variable tilt angles swash-platestroke control and rotary port-face hydraulic distribution control,characterized by a rotary swash-plate member in which piston-thrusttorque reaction and developed torque on the rotary swashplate member istransmitted directly to a rotary main driving shaft by sphericallyjointed links interconnecting said rotary swash-plate member to saidshaft, a cylinder barrel being located on a sleeve loosely keyed to saiddriving shaft so that piston-thrust torque reaction and developed torqueis not transmitted directly from said cylinder barrel to said drivingshaft, and the rotary swash-plate member being supported by a thrustbearing on a non-rotating tilt member.

2. An axial piston pump/motor according to claim 1,

in which the links are of flattened C formation.

1. An axial piston pump/motor having variable tilt angles swashplatestroke control and rotary port-face hydraulic distribution control,characterized by a rotary swash-plate member in which piston-thrusttorque reaction and developed torque on the rotary swash-plate member istransmitted directly to a rotary main driving shaft by sphericallyjointed links interconnecting said rotary swash-plate member to saidshaft, a cylinder barrel being located on a sleeve loosely keyed to saiddriving shaft so that piston-thrust torque reaction and developed torqueis not transmitted directly from said cylinder barrel to said drivingshaft, and the rotary swash-plate member being supported by a thrustbearing on a non-rotating tilt member.
 2. An axial piston pump/motoraccording to claim 1, in which the links are of flattened ''''C''''formation.